Conventionally, there has been a dimming device that determines whether or not a current value of a load current is abnormal by comparing a measured value of the load current with a specified value in a state where the operation mode of a control unit for controlling illumination loads is switched to an inspection mode in which all of the illumination loads are turned on (see, e.g., Japanese Unexamined Patent Application Publication No. 2012-69398 (JP2012-69398A))
In the dimming device described in JP2012-69398A, when measuring the current value of the load current, the operation mode is switched from a normal mode to the inspection mode in which all of the illumination loads are turned on. However, e.g., in 24-hour commercial facilities, since it is difficult to switch the operation mode from the normal mode to the inspection mode, there is a demand to know whether or not a dimming control unit is overloaded even in a state where the illumination loads are turned on in the normal mode.